The primary head worn, night vision devices used by the United States (US) military are night vision goggles (NVGs). Although these devices can be monocular (one eye looking at an image), biocular (two eyes looking at the same image), or binocular (two eyes looking at two images) in design, conventional NVGs all use image intensification (I2) tube technology. An I2 tube multiplies ambient visible and near IR light several thousands of times. I2 tube technology allows a user to see and operate in very low light conditions. In extreme low light conditions additional near IR illumination can be used. Although this near IR illumination can be seen with the aid of a night vision device, the near IR illumination is invisible to unaided human eyes.
Current night vision technologies use the visible (400-780 nanometer), near infrared (IR) (780 nanometer-1 micron), mid wave IR (3-5 micron), and long wave IR (8-12 micron) bands. The proliferation of night vision technologies has placed devices into the hands of US adversaries, thereby reducing the US military's advantage during low light operations.
The strength of night vision goggles is also one of its disadvantages. The I2 tube is inherently a direct view system. Light enters objective optics on one end of a night vision device and is focused onto the I2 tube. The light is amplified by the I2 tube and exits the device through eyepiece optics. I2 tube night vision devices can be small, light-weight, and rugged. One disadvantage with I2 tube night vision devices is I2 tube night vision devices can not generate an image as a video signal that can be displayed on a monitor or transmitted externally. The I2 tube is also sensitive to too much light. Too much light can over saturate the I2 tube and prevent the user from seeing any scene detail. This problem is called blooming or a halo effect. Therefore, an I2 device can only be used in low-light conditions. In very low-light conditions, additional near IR illumination or lasers can be used. This active illumination technique can be seen by all I2 devices. So if an adversary has an I2 device, any opposing force using near IR illuminators or lasers may inadvertently disclose their position. Additional disadvantages are the narrow applications the night vision devices are designed for. These devices are primarily mobility devices with a fixed field of view, e.g., 40°.
An example of an I2 night vision device is the Army's AN/PVS-14. The AN/PVS-14 is a monocular device that can be handheld, mounted onto a helmet or on a weapon. However, the AN/PVS-14 does not have video output, power input, or external video input capabilities. Additionally, the AN/PVS-14 does not accept alternative objective lenses other than magnifiers that narrow the field of view. Another example of a monocular night vision I2 device is a commercial off the shelf (COTS) Pocket Scope MK-880 sold by OSTI. Although similar to the AN/PVS-14, the Pocket Scope MK-880 can accept external power and alternative objective lenses. But the Pocket Scope MK-880 is still susceptible to too much light, the inability to export the amplified image, and the inability to display external video.
Irvine Sensors has developed a Personal Miniature Thermal Viewer (PMTV). The PMTV is a compact thermal imager with an integrated display. The PMTV is compact, direct-view, battery operated, and can produce imagery in the mid-wave IR band. However, the PMTV can not display an external video.
What is needed is an alternative imaging device that utilizes wavelengths of the electro-magnetic (EM) spectrum currently unused in military environments.